Testing motor protection relays with three phase high current injection

The latest generation of inline protections for three phase motors include sophisticated and powerful relaying functions to provide flexibility and to avoid expensive damages from common failures like overload or phase unbalance. However, testing these devices can be difficult or impossible if you do not have three phase high current injection test equipment.

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What is three phase high current injection?

Basically, three phase high current injection consists of applying three phase voltage to any three-phase device or element in an electrical installation with the intention to test the device’s behavior under a variety of situations, typically overcurrent, overheating and phase failure, or to verify the accuracy of current and / or phase angle meters. Three phase high current injection uses low voltage in order to keep the test equipment reasonably small and lightweight, so to make these tasks practical and safe; therefore the tested device must be previously isolated from any other power sources and consumers.

Why should I need three phase high current injection?

Most modern inline motor protection relays take the operating power from the three-phase line and are sensitive to phase unbalance, so you need three phase current just to make them work. The older version of these devices based their operation on the heating caused by the current flow to bi-metallic components, so they could be tested with a basic single-phase current injector, one pole at a time. However the type of protection offered and the range of motor characteristics covered by a single relay was too limited.

The new generation of relays feature a more comprehensive set of protection and control functions, and offer a wider choice of user-selectable settings which makes them suitable for a larger range of motor types; phase supervision is one of the new built-in features, so the user does not need to add a specialized device to protect the motor against phase failure or wiring mistakes.

In order to test all these functions, an instrument capable to provide real three phase high current injection is needed that will allow you to arbitrarily simulate diverse faulty conditions quickly and accurately.

The TriRaptor’s three phase high current injection will help you reduce the time for motor relay testing dramatically while increasing accuracy, safety and the overall quality of your job.

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We are a leading company that designs, manufactures and market a range of electronic products and solutions for electrical testing, tests and measurement equipment related to the commissioning and maintenance in substations, power plants and energy systems.